Bitbucket Local Runner failing on build

[Jez Cordonnier]

I have got a local runner on a Debian server which was working until recently. The pipeline is super small now just to do the bare minimum (see below).

The runner is up and running and Bitbucket is able to see the runner as active. When I run a pipeline, it starts the clone and I can see the logs progressing (so its definitely processing the action), until it gets to the build step. At this point, it just fails. No feedback in the GUI and no clear reason in the logs on the server. 

This was working fine for months before it suddenly didn't. Something must have changed, but I'm unsure what it could be. 

The worker is the Java linux shell. (I don't want to install docker just for this).

This is the runner log where it exists. Clone above is fine.

Generating build script.
Adding log file: /home/user/atlassian-bitbucket-pipelines-runner/bin/../temp/XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXX/tmp/build12306387268082114998.log
Executing build script in native script.
Script exited with exit code: 1

In the `tmp` directory these are the only log files. Build and CacheTeardown are both empty.

0     build12306387268082114998.log
0     cacheTeardown13785616896405678645.log
1053  clone12982692299869077354.log
2061  cloneScript626750428785171366.sh

bitbucket-pipeline.yml

definitions:
  steps:
    - step: &minimal-test
        name: Minimal Test
        runs-on:
          - self.hosted
          - linux.shell
          - staging
        script:
          - echo "test"

pipelines:
  custom:
    test:
      - step: *minimal-test

Any ideas would be greatly welcomed.